This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Objective: To determine the factors underlying quality paternal care in male marmosets. With poor parenting or parental absence, there are a number of psychosocial disorders that confound human health. Marmosets are one of the few mammalian species whose social organization/family structure bears resemblance to that of humans. These studies are designed to determine the hormonal pathway for priming paternal care behaviors in biparental males who show extensive parental care. Olfactory cues can exert priming effects on many mammalian species. Paternally experienced marmosets, Callithrix jacchus, exposed to direct isolated olfactory contact with their own infant's scent show rapid decreases in testosterone levels within 20 minutes, whereas paternally inexperienced males do not. We tested whether there is a differential steroid response to exposure of infant scent from dependent infants (own and novel) and independent infants (own and novel). We examined the serum levels of estradiol, estrone, testosterone, dihydrotestosterone (DHT), and combined estrogens and androgens in eight male marmosets 20 minutes after exposure to isolated infant scent. Testosterone levels were significantly influenced by the relatedness of the scent;testosterone levels were significantly lower with exposure to own infant scent than a novel infant scent. Estrogen levels elevated significantly in response to own infant scent. Significant differences in testosterone levels were not seen as a factor of age for the related infant but increased estrogens were significant. These results suggest that marmoset fathers are responsive to priming cues from related infants and that responsiveness may last beyond the period of infant dependence. We have also found that increased estradiol significantly stimulates males to be more attentive to infant distress signals in na[unreadable]ve males. Males who have not been fathers before show little responsiveness to infant stimuli while experienced fathers show significant response to infant stimuli. We are currently assessing the variation in pituitary levels of dopamine, oxytocin, vasopressin and prolactin from intact anterior and posterior pituitaries as well as each pituitary cultured separately for experienced and na[unreadable]ve males. Initial results are revealing significant differences between experienced fathers and na[unreadable]ve males in their levels of prolactin and oxytocin but not vasopressin. Experienced fathers have significantly higher prolactin and oxytocin than na[unreadable]ve fathers. This research project relies on WNPRC Assay Services, Animal Services, and Clinical Pathology. PUBLICATION: Ziegler TE, Peterson LJ, Sosa ME, Barnard AM. Differential endocrine responses to infant odors in common marmoset (Callithrix jacchus) fathers. Hormones &Behavior . Dec 9 2010 [Epub ahead of print] PMID: 21145893. PMC3040271.